Polyacrylate elastomers are well known specialty elastomers having extensive utility in the automative industry as gasketing material, oil seals, O-rings, transmissions seals, and the like. In effect such elastomers are employed where resistance to hot oil is important and in such usage the retention of physical properties is of paramount importance.
There are available a number of polyacrylate elastomers finding use in the automotive industry and other industries. Note U.S. Pat. No. 3,201,373, Kaizerman, which discloses polyacrylate elastomers derived from copolymerization of a major proportion of a lower alkyl acrylate with vinyl chloroacetate. Similarly, P. Fram in the Encyclopedia of Polymer Science and Technology 1, 226 (1964) describes polyacrylates wherein other halogen containing comonomers, such as vinyl chloroethyl ether, are copolymerized with alkyl acrylates. Polyacrylates are described which are composed of, in addition to alkyl acrylates, alkoxy-alkyl acrylates, cyanoalkyl acrylates and alkylthioalkylacrylates. Note U.S. Pat. No. 3,450,681, Gobran et al, and U.S. Pat. No. 3,488,331, Joregenson. The status of vulcanizable polyacrylate elastomers up to the present time is reviewed by T. M. Vial in Rubber Chemistry and Technology, "Rubber Reviews", April, 1977. These elastomers are vulcanizable by a variety of means which is also summarized in the article.
The property of acrylate elastomers which is probably most important in their application is oil resistance, a term encompassing several properties, including volume swell and retention of physical properties after exposure to hot oil for a period of time. This exposure usually involves softening, loss of modulus and gain in elongation due to plasticizing or the swelling action of the oil, as well as thermal degradation.
However, in spite of the generally favorable oil resistance of polyacrylate elastomers there is always a search for means whereby oil resistance can be improved to obtain longer life in service. Anything which provides better retention of properties on exposure to hot oil, other things being equal, is desirable. The present invention represents the culmination of a series of investigations conducted largely by the inventors and their associates directed to improving the oil resistance of polyacrylate elastomers.
Accordingly, it is a primary object of the present invention to provide vulcanizable polyacrylate elastomer compositions having improved resistance to hydrocarbon oils.
Another object of the present invention is to provide a method for improving the oil resistance of vulcanizable polyacrylate elastomer compositions.
It is a further object of the present invention to provide a vulcanized elastomer having improved resistance to hydrocarbon oils.
Generally then, it is an object of this invention to provide an improved vulcanized elastomer which retains its physical properties when employed in a hot oil environment. This retention results in a significant lengthening of the service life of materials prepared from such elastomers.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be realized by practice of the invention, the objects and advantages being realized and attained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.